Is it possible to turn off grid in orthographic view?
Assuming you have 'Grid Floor' turned off as moonboots shows, there's a quick trick .. when in one of the standard Orthographic Views, tap 46 on your Numpad..(rotating your view by + and - 15 degrees). This converts your standard Orthographic View to a User Orthographic View, from exactly the same angle, and the ortho background grid disappears